PO.MCB07.03 · 分子与细胞生物学
APOBEC4——p53依赖性肿瘤抑制的新型调控因子
APOBEC4, a novel regulator of p53-dependent tumor suppression
作者与单位 Authors & Affiliations
摘要 Abstract
中文摘要
引言：肿瘤抑制蛋白p53作为一种转录因子，可激活下游靶基因（如p21、PUMA、NOXA、BAX和GADD45alpha），诱导细胞周期停滞、衰老、凋亡等生物学过程。然而，p53活性在肿瘤发生过程中常受到损害，约半数人类癌症携带TP53突变。即使在保留野生型p53（wtp53）的肿瘤中，p53也会通过多种机制被降解或抑制，包括其E3泛素连接酶MDM2的过表达。MDM2拮抗剂（如Nutlin-3a）是恢复p53功能、抑制肿瘤生长的有前景的策略。然而，调控MDM2拮抗剂疗效及p53介导的肿瘤抑制的因素/生物标志物仍知之甚少。识别此类因素并理解其功能对于优化p53靶向治疗至关重要。
实验方法：利用人类全基因组shRNA文库筛选，我们试图在经Nutlin-3a处理的骨肉瘤U2OS细胞中识别调控p53依赖性肿瘤抑制的因素。此次筛选及后续验证揭示APOBEC4是Nutlin-3a处理后p53介导的集落抑制的关键因素。在多种p53功能完整的癌细胞系中，敲除APOBEC4减弱了Nutlin-3a诱导的p53转录激活，并降低了p53依赖性细胞周期停滞和凋亡。为探究其潜在机制，我们进行了免疫共沉淀（Co-IP）和邻近连接实验（PLA），结果显示APOBEC4与p53结合。此外，敲低APOBEC4后，由H2O2和致癌性HRAS G12V诱导的细胞衰老也有所降低。重要的是，敲除APOBEC4在体内显著减弱了Idasanutlin介导的肿瘤抑制。
结论：我们的研究结果识别出APOBEC4是p53依赖性细胞周期停滞、衰老、凋亡及肿瘤抑制的新型调控因子，凸显了其作为p53靶向治疗生物标志物的潜力。
查看英文原文 English abstract
Introduction: The tumor suppressor protein p53 (p53) functions as a transcription factor that activates downstream target genes such as p21, PUMA, NOXA, BAX, and GADD45alpha to induce cell cycle arrest, senescence, apoptosis, and other biological processes. However, p53 activity is frequently compromised during tumorigenesis, with approximately half of human cancers harboring TP53 mutations. Even in tumors retaining wild-type p53 (wtp53), it gets degraded or inhibited through various mechanisms, including the overexpression of its E3 ubiquitin ligase MDM2. MDM2 antagonists such as Nutlin-3a are promising strategies to restore p53 function and inhibit tumor growth. Yet, factors/biomarkers regulating the efficacy of MDM2 antagonists and p53-mediated tumor suppression remain poorly understood. Identifying such factors and understanding their functions are essential for optimizing p53-targeted therapies.
Experimental Procedures: Using a human whole-genome shRNA library screen, we sought to identify factors regulating p53-dependent tumor suppression in osteosarcoma U2OS cells treated with Nutlin-3a. This screening and subsequent validation revealed APOBEC4 as a critical factor for p53-mediated colony suppression following Nutlin-3a treatment. Deletion of APOBEC4 attenuated Nutlin-3a-induced p53 transcriptional activation and reduced p53-dependent cell cycle arrest and apoptosis across multiple p53-proficient cancer cell lines. To investigate the underlying mechanism, we performed co-immunoprecipitation (Co-IP) and proximity ligation assays (PLA), which revealed APOBEC4 binds to p53. Furthermore, cellular senescence induced by H 2 O 2 and oncogenic HRAS G12V , was also reduced upon APOBEC4 knockdown. Importantly, APOBEC4 deletion significantly attenuated Idasanutlin-mediated tumor suppression in vivo .
Conclusion: Our findings identify APOBEC4 as a novel regulator of p53-dependent cell cycle arrest, senescence, apoptosis, and tumor suppression, highlighting its potential as a biomarker for p53-targeted therapies.
利益披露 Disclosure
D. Thapa, None..
A. Parrales Briones, None..
E. Thoenen, None..
S. Nishikawa, None..
J. Vivian, None..
T. Iwakuma, None.